from django.db import connection
from django.db.models import Case, Count, F, FilteredRelation, Q, When
from django.test import TestCase
from django.test.testcases import skipUnlessDBFeature

from .models import Author, Book, Borrower, Editor, RentalSession, Reservation


class FilteredRelationTests(TestCase):

    @classmethod
    def setUpTestData(cls):
        cls.author1 = Author.objects.create(name='Alice')
        cls.author2 = Author.objects.create(name='Jane')
        cls.editor_a = Editor.objects.create(name='a')
        cls.editor_b = Editor.objects.create(name='b')
        cls.book1 = Book.objects.create(
            title='Poem by Alice',
            editor=cls.editor_a,
            author=cls.author1,
        )
        cls.book1.generic_author.set([cls.author2])
        cls.book2 = Book.objects.create(
            title='The book by Jane A',
            editor=cls.editor_b,
            author=cls.author2,
        )
        cls.book3 = Book.objects.create(
            title='The book by Jane B',
            editor=cls.editor_b,
            author=cls.author2,
        )
        cls.book4 = Book.objects.create(
            title='The book by Alice',
            editor=cls.editor_a,
            author=cls.author1,
        )
        cls.author1.favorite_books.add(cls.book2)
        cls.author1.favorite_books.add(cls.book3)

    def test_select_related(self):
        qs = Author.objects.annotate(
            book_join=FilteredRelation('book'),
        ).select_related('book_join__editor').order_by('pk', 'book_join__pk')
        with self.assertNumQueries(1):
            self.assertQuerysetEqual(qs, [
                (self.author1, self.book1, self.editor_a, self.author1),
                (self.author1, self.book4, self.editor_a, self.author1),
                (self.author2, self.book2, self.editor_b, self.author2),
                (self.author2, self.book3, self.editor_b, self.author2),
            ], lambda x: (x, x.book_join, x.book_join.editor, x.book_join.author))

    def test_select_related_foreign_key(self):
        qs = Book.objects.annotate(
            author_join=FilteredRelation('author'),
        ).select_related('author_join').order_by('pk')
        with self.assertNumQueries(1):
            self.assertQuerysetEqual(qs, [
                (self.book1, self.author1),
                (self.book2, self.author2),
                (self.book3, self.author2),
                (self.book4, self.author1),
            ], lambda x: (x, x.author_join))

    def test_without_join(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
            ),
            [self.author1, self.author2]
        )

    def test_with_join(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
            ).filter(book_alice__isnull=False),
            [self.author1]
        )

    def test_with_join_and_complex_condition(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_alice=FilteredRelation(
                    'book', condition=Q(
                        Q(book__title__iexact='poem by alice') |
                        Q(book__state=Book.RENTED)
                    ),
                ),
            ).filter(book_alice__isnull=False),
            [self.author1]
        )

    def test_internal_queryset_alias_mapping(self):
        queryset = Author.objects.annotate(
            book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
        ).filter(book_alice__isnull=False)
        self.assertIn(
            'INNER JOIN {} book_alice ON'.format(connection.ops.quote_name('filtered_relation_book')),
            str(queryset.query)
        )

    def test_with_multiple_filter(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_editor_a=FilteredRelation(
                    'book',
                    condition=Q(book__title__icontains='book', book__editor_id=self.editor_a.pk),
                ),
            ).filter(book_editor_a__isnull=False),
            [self.author1]
        )

    def test_multiple_times(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_title_alice=FilteredRelation('book', condition=Q(book__title__icontains='alice')),
            ).filter(book_title_alice__isnull=False).filter(book_title_alice__isnull=False).distinct(),
            [self.author1]
        )

    def test_exclude_relation_with_join(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_alice=FilteredRelation('book', condition=~Q(book__title__icontains='alice')),
            ).filter(book_alice__isnull=False).distinct(),
            [self.author2]
        )

    def test_with_m2m(self):
        qs = Author.objects.annotate(
            favorite_books_written_by_jane=FilteredRelation(
                'favorite_books', condition=Q(favorite_books__in=[self.book2]),
            ),
        ).filter(favorite_books_written_by_jane__isnull=False)
        self.assertSequenceEqual(qs, [self.author1])

    def test_with_m2m_deep(self):
        qs = Author.objects.annotate(
            favorite_books_written_by_jane=FilteredRelation(
                'favorite_books', condition=Q(favorite_books__author=self.author2),
            ),
        ).filter(favorite_books_written_by_jane__title='The book by Jane B')
        self.assertSequenceEqual(qs, [self.author1])

    def test_with_m2m_multijoin(self):
        qs = Author.objects.annotate(
            favorite_books_written_by_jane=FilteredRelation(
                'favorite_books', condition=Q(favorite_books__author=self.author2),
            )
        ).filter(favorite_books_written_by_jane__editor__name='b').distinct()
        self.assertSequenceEqual(qs, [self.author1])

    def test_values_list(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
            ).filter(book_alice__isnull=False).values_list('book_alice__title', flat=True),
            ['Poem by Alice']
        )

    def test_values(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
            ).filter(book_alice__isnull=False).values(),
            [{'id': self.author1.pk, 'name': 'Alice', 'content_type_id': None, 'object_id': None}]
        )

    def test_extra(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
            ).filter(book_alice__isnull=False).extra(where=['1 = 1']),
            [self.author1]
        )

    @skipUnlessDBFeature('supports_select_union')
    def test_union(self):
        qs1 = Author.objects.annotate(
            book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
        ).filter(book_alice__isnull=False)
        qs2 = Author.objects.annotate(
            book_jane=FilteredRelation('book', condition=Q(book__title__iexact='the book by jane a')),
        ).filter(book_jane__isnull=False)
        self.assertSequenceEqual(qs1.union(qs2), [self.author1, self.author2])

    @skipUnlessDBFeature('supports_select_intersection')
    def test_intersection(self):
        qs1 = Author.objects.annotate(
            book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
        ).filter(book_alice__isnull=False)
        qs2 = Author.objects.annotate(
            book_jane=FilteredRelation('book', condition=Q(book__title__iexact='the book by jane a')),
        ).filter(book_jane__isnull=False)
        self.assertSequenceEqual(qs1.intersection(qs2), [])

    @skipUnlessDBFeature('supports_select_difference')
    def test_difference(self):
        qs1 = Author.objects.annotate(
            book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
        ).filter(book_alice__isnull=False)
        qs2 = Author.objects.annotate(
            book_jane=FilteredRelation('book', condition=Q(book__title__iexact='the book by jane a')),
        ).filter(book_jane__isnull=False)
        self.assertSequenceEqual(qs1.difference(qs2), [self.author1])

    def test_select_for_update(self):
        self.assertSequenceEqual(
            Author.objects.annotate(
                book_jane=FilteredRelation('book', condition=Q(book__title__iexact='the book by jane a')),
            ).filter(book_jane__isnull=False).select_for_update(),
            [self.author2]
        )

    def test_defer(self):
        # One query for the list and one query for the deferred title.
        with self.assertNumQueries(2):
            self.assertQuerysetEqual(
                Author.objects.annotate(
                    book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
                ).filter(book_alice__isnull=False).select_related('book_alice').defer('book_alice__title'),
                ['Poem by Alice'], lambda author: author.book_alice.title
            )

    def test_only_not_supported(self):
        msg = 'only() is not supported with FilteredRelation.'
        with self.assertRaisesMessage(ValueError, msg):
            Author.objects.annotate(
                book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
            ).filter(book_alice__isnull=False).select_related('book_alice').only('book_alice__state')

    def test_as_subquery(self):
        inner_qs = Author.objects.annotate(
            book_alice=FilteredRelation('book', condition=Q(book__title__iexact='poem by alice')),
        ).filter(book_alice__isnull=False)
        qs = Author.objects.filter(id__in=inner_qs)
        self.assertSequenceEqual(qs, [self.author1])

    def test_with_foreign_key_error(self):
        msg = (
            "FilteredRelation's condition doesn't support nested relations "
            "(got 'author__favorite_books__author')."
        )
        with self.assertRaisesMessage(ValueError, msg):
            list(Book.objects.annotate(
                alice_favorite_books=FilteredRelation(
                    'author__favorite_books',
                    condition=Q(author__favorite_books__author=self.author1),
                )
            ))

    def test_with_foreign_key_on_condition_error(self):
        msg = (
            "FilteredRelation's condition doesn't support nested relations "
            "(got 'book__editor__name__icontains')."
        )
        with self.assertRaisesMessage(ValueError, msg):
            list(Author.objects.annotate(
                book_edited_by_b=FilteredRelation('book', condition=Q(book__editor__name__icontains='b')),
            ))

    def test_with_empty_relation_name_error(self):
        with self.assertRaisesMessage(ValueError, 'relation_name cannot be empty.'):
            FilteredRelation('', condition=Q(blank=''))

    def test_with_condition_as_expression_error(self):
        msg = 'condition argument must be a Q() instance.'
        expression = Case(
            When(book__title__iexact='poem by alice', then=True), default=False,
        )
        with self.assertRaisesMessage(ValueError, msg):
            FilteredRelation('book', condition=expression)

    def test_with_prefetch_related(self):
        msg = 'prefetch_related() is not supported with FilteredRelation.'
        qs = Author.objects.annotate(
            book_title_contains_b=FilteredRelation('book', condition=Q(book__title__icontains='b')),
        ).filter(
            book_title_contains_b__isnull=False,
        )
        with self.assertRaisesMessage(ValueError, msg):
            qs.prefetch_related('book_title_contains_b')
        with self.assertRaisesMessage(ValueError, msg):
            qs.prefetch_related('book_title_contains_b__editor')

    def test_with_generic_foreign_key(self):
        self.assertSequenceEqual(
            Book.objects.annotate(
                generic_authored_book=FilteredRelation(
                    'generic_author',
                    condition=Q(generic_author__isnull=False)
                ),
            ).filter(generic_authored_book__isnull=False),
            [self.book1]
        )


class FilteredRelationAggregationTests(TestCase):

    @classmethod
    def setUpTestData(cls):
        cls.author1 = Author.objects.create(name='Alice')
        cls.editor_a = Editor.objects.create(name='a')
        cls.book1 = Book.objects.create(
            title='Poem by Alice',
            editor=cls.editor_a,
            author=cls.author1,
        )
        cls.borrower1 = Borrower.objects.create(name='Jenny')
        cls.borrower2 = Borrower.objects.create(name='Kevin')
        # borrower 1 reserves, rents, and returns book1.
        Reservation.objects.create(
            borrower=cls.borrower1,
            book=cls.book1,
            state=Reservation.STOPPED,
        )
        RentalSession.objects.create(
            borrower=cls.borrower1,
            book=cls.book1,
            state=RentalSession.STOPPED,
        )
        # borrower2 reserves, rents, and returns book1.
        Reservation.objects.create(
            borrower=cls.borrower2,
            book=cls.book1,
            state=Reservation.STOPPED,
        )
        RentalSession.objects.create(
            borrower=cls.borrower2,
            book=cls.book1,
            state=RentalSession.STOPPED,
        )

    def test_aggregate(self):
        """
        filtered_relation() not only improves performance but also creates
        correct results when aggregating with multiple LEFT JOINs.

        Books can be reserved then rented by a borrower. Each reservation and
        rental session are recorded with Reservation and RentalSession models.
        Every time a reservation or a rental session is over, their state is
        changed to 'stopped'.

        Goal: Count number of books that are either currently reserved or
        rented by borrower1 or available.
        """
        qs = Book.objects.annotate(
            is_reserved_or_rented_by=Case(
                When(reservation__state=Reservation.NEW, then=F('reservation__borrower__pk')),
                When(rental_session__state=RentalSession.NEW, then=F('rental_session__borrower__pk')),
                default=None,
            )
        ).filter(
            Q(is_reserved_or_rented_by=self.borrower1.pk) | Q(state=Book.AVAILABLE)
        ).distinct()
        self.assertEqual(qs.count(), 1)
        # If count is equal to 1, the same aggregation should return in the
        # same result but it returns 4.
        self.assertSequenceEqual(qs.annotate(total=Count('pk')).values('total'), [{'total': 4}])
        # With FilteredRelation, the result is as expected (1).
        qs = Book.objects.annotate(
            active_reservations=FilteredRelation(
                'reservation', condition=Q(
                    reservation__state=Reservation.NEW,
                    reservation__borrower=self.borrower1,
                )
            ),
        ).annotate(
            active_rental_sessions=FilteredRelation(
                'rental_session', condition=Q(
                    rental_session__state=RentalSession.NEW,
                    rental_session__borrower=self.borrower1,
                )
            ),
        ).filter(
            (Q(active_reservations__isnull=False) | Q(active_rental_sessions__isnull=False)) |
            Q(state=Book.AVAILABLE)
        ).distinct()
        self.assertEqual(qs.count(), 1)
        self.assertSequenceEqual(qs.annotate(total=Count('pk')).values('total'), [{'total': 1}])
